1. Field of the Invention
The present invention relates, in general, to the fixation of bone fractures and, more particularly, to the fixation of bone fractures having small fragments proximate a terminal end of a bone.
2. Description of Related Art
Plates and screws are well accepted techniques for fixation of fractures. The standard bone plate is a planar bar of material, usually metal, having circular and/or slotted holes through which bone screws are placed. The bone plate is used to span a fracture and fixation screws are placed through holes in the bone plate positioned on either side of the fracture to secure the bone fragments the plate.
One variation of the standard bone plate is to modify the configuration of the screw holes to help provide compression across the fracture as the screw is placed. Another variation is to include female threads within the perimeter of the bone plate's screw holes, engaging male threads on the head of the screw to lock the screw to the plate.
Difficulties in using bone plates may arise in certain fractures occurring relatively close to the end of a bone, creating a relatively small end fragment. In this situation, there may simply be not enough bone available in the end fragment to accommodate a sufficient number of screws to achieve secure fixation. As a result, a surgeon using a conventional bone plate may use a suboptimal number of screws, which can lead to postoperative failure.
One example of a fracture occurring relatively close to the end of a bone is a fracture of the lateral malleolus, the terminal portion of the fibula that is present on the outside of the ankle, occurring close to its tip. In such situations, only a very small distal fragment may be present, providing inadequate room for more than one or two screws to be placed. Moreover, since the deep portion of this bone is a part of the overall ankle joint, screws cannot be placed through both cortices, as is commonly practice with plate/screw techniques. Accordingly, the surgeon may be faced with the undesirable situation of having the patient leave the operating room with only one or two screws engaging a bone surface directly under a bone plate.
In the past, one technique surgeons have used in an attempt to provide enhanced fixation or grip of a small terminal bone fragment is to begin with a standard plate and cut the plate transversely across at its last screw hole. Using a pair of surgical pliers or other suitable instrument, the remaining bone plate material on opposing sides of the partially remaining hole is bent around the outer surface of the terminal bone fragment. To some degree, this helps supplement the tenuous fixation provided by only one or two screws in the small terminal fragment. However, this terminal bone fragment may still remain far from being well secured.
In another previous technique disclosed in “Use of Zuelzer Hook Plate in the Treatment of Olecranon Fractures” by Wesely, Barenfeld, and Eisenstein, The Journal of Bone & Joint Surgery, Volume 58-A, Issue No 6, September 1976, pages 859-863, a further modification of this technique is described in which a flat plate is pre-contoured with two hooks at one end. The hooks are bent so that they are parallel to the longitudinal axis of the flat plate. The plate is applied to a fractured bone such as the olecranon by manually pressing the hooks into the bone and fixing the plate to the bone surface with screws. Although this technique adds the theoretical advantage of penetration of the terminal fragment with the hooks, if this plate is applied to an anatomic site in which the bone flares out at the terminal end, since the hooks are parallel to the linear axis of the plate, as the hooks are impacted, the plate will not sit flush with the bone surface past the flare at the terminal end but rather come to lie in a position that sits off the bone. In addition, this technique does not address the problem of creating holes in the bone at the correct depth for engagement by the hooks, but rather relies on manual pressure on the plate to attempt penetration of the bone by the hooks at whatever level they happen to contact. As can be noted by the examples in this article, the hooks may fail to penetrate the bone resulting in less than satisfactory engagement and fixation of the terminal fragment by the hooks as well as prominence of the hooks in the soft tissue because of incomplete seating. Finally, since these implants have hooks that extend an equal distance from the end of the plate, this design does not allow completely seating of both hooks in the common situation in which the bone surface at the terminal end is at an angle to the plane that is perpendicular to the long axis of the bone.
Accordingly, it is an object of the present invention to provide a bone plate that adequately secures a small bone fragment at a terminal end of a bone.
It is a further object of the present invention to provide a bone plate that can be seated flush against a bone characterized by a flare at the terminal segment, yet sill providing full engagement of the small terminal fragment by complete seating of one or more hooks into bone. It is a further object of the present invention to provide a means to create pilot holes in the terminal fragment for engagement by the hooks in the plate such that the hook or hooks in the plate engage the bone at the correct depth and trajectory so as to direct the plate to advance both longitudinally as well as drop down against the surface of the bone as it is seated.
It is another object of the present invention to provide a design that has a contour that approximates the flare of the terminal segment of a bone as well as provides one or more hooks that are angled along an axis that approximates the best linear fit approximation of such flare.
It is another object of the present invention to provide a drill guide facilitating accurate placement of a bone plate proximate a terminal end of a bone.
These and other objects and features of the present invention will become apparent in view of the present specification, drawing and claims.